""the IG plans to liaise with regulatory bodies to improve compliance targets""
Regulatory bodies absolutely do not care about W3C. Hell, they barely care about the IETF, IEEE, ICANN, etc.
I'm all for pushing for sustainability, but look at the other interest groups. For example, privacy. Cloudflare just published an article talking about post-quantum crypto [1] where they talk about how wild a percent of traffic would be just cert exchange (and, currently already is). There will always be competing interests, so a body that only exists to checks notes talk about ""sustainability"" on the web feels moot.
They explicitly say hardware is out of scope. Cool. So software. The only way to help sustainability is to use less or make it more efficient. Less never happens, and efficiency isn't a concern above ad revenue for literally anyone.
Honestly, I'm inclined to see this as actively harmful more than anything. Putting out statements about sustainability just dilutes the waters on web issues they might have real pull in, like standards for user privacy that DO help with sustainability. For example, making it easier to choose what content gets delivered cough DNS blackhole adblock cough means less data being transfered.
I still wish this group the best and hope that they can discuss actions of other groups (Such as the Media and Entertainment Interest Group) in context of their choice of standards impact on processing power requirements.
Honestly, reading the manifesto [2] just makes me more angry. It doesn't say anything. Go read some solar-punk manifestos by people on the Indie Web or in Solarpunk culture. Those at least say something. This is just marketing fluff for the sponsors at the bottom of the page.
[1] https://blog.cloudflare.com/another-look-at-pq-signatures/ [2] https://www.sustainablewebmanifesto.com